Complex organic matter discovered in the vicinity of a young star

Complex organic matter discovered in the vicinity of a young star
Complex organic matter discovered in the vicinity of a young star

In the protoplanetary disk of a young star in the direction of the constellation Orion, astronomers were able to see several complex organic molecules. In this they were helped by the special character of the star.


V883 Orionis is a young star located approximately 1,300 light years from Earth in the direction of the constellation Orion. This star is experiencing a so-called FU Orion-type flare - a sudden increase in brightness due to a bursting stream of material flowing from the protoplanetary disk towards the star. This rare occurrence allowed ALMA to register five complex organic molecules in the vicinity of V883 Orionis. The study is described in the journal Nature Astronomy.

In the protoplanetary disks of young stars, various molecules are frozen in ices around micrometer-sized dust particles. The sudden flash of V883 Orionis heats up the disk and sublimates ice, which eventually releases the molecules into gas.

The area of ​​the disk where the temperature reaches the temperature of sublimation of molecules is called the "snow line". The radii of snow lines are usually on the order of several AU. (astronomical units) around young stars, but in the case of flare stars, they can be up to 10 times larger.


Schematic representation of the composition of protoplanetary disks in the normal state and in the flare phase / © National Astronomical Observatory of Japan

“It is difficult to get a snapshot of a disk that is several au. with today's telescopes, says Kyung Hee University astronomer Dr. Jung Eun Lee. “However, around flare stars, ice melts in a wider region of the disk, making it easier to see the distribution of molecules. We are interested in the proliferation of complex organic molecules as the building blocks of life."

Thanks to the keen eyesight of ALMA and the magnified snow line of the flaring star, Dr. Lee and his co-authors were able to register and analyze five different complex organic molecules: methanol (CH3OH), acetone (CH3COCH3), acetonitrile (CH3CN), acetaldehyde (CH3CHO) and methyl formate (CH3OCHO) … Astronomers also gained spatial distribution of methanol and acetaldehyde.

"These molecules are distributed in a ring-shaped structure with a radius of 60 AU, which is twice the size of Neptune's orbit," the researchers explain. "Inside this ring, the molecules are invisible, as they are obscured by the dusty material, and outside it, they are invisible because they are frozen."

“Because rocky and icy planets are made of solid material, the chemical composition of the solid in the disks is of particular importance,” said University of Tokyo astronomer Dr. Yuri Aikawa. "Flash is a unique opportunity to explore fresh sublimates, and hence the composition of solids."

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